Restore the interrupted thread status in the provided backoff policies

[mlichtblau]

It is good practice to restore the interrupted flag of the current thread when InterruptedException cannot be thrown.

From Java Concurrency in Practice¹:

Sometimes you cannot throw InterruptedException, for instance when your code is part of a Runnable. In these situations, you must catch InterruptedException and restore the interrupted status by calling interrupt on the current thread

The provided backoff policies (e.g. FixedBackOffPolicy, ExponentialBackOffPolicy) throw a BackOffInterruptedException without restoring the flag.

Do you think it is possible to restore the flag before throwing the runtime exception?
I can open a PR.

Thank you!

Footnotes

1. Google Books ↩

[garyrussell]

Good catch, yes, this is a bug. A PR would be welcome.

[mlichtblau]

Thanks, I opened #387